Maximizing energy efficiency in hotel HVAC systems: An energy modelling approach to comparing Chilled water and Variable Refrigerant Flow (VRF) systems

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 05 | May 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 1153
Maximizing energy efficiency in hotel HVAC systems: An energy
modelling approach to comparing Chilled water and Variable
Refrigerant Flow (VRF) systems
Mohammad Furqan, Naveen, Priyanshu Verma
MOHAMMAD FURQAN, B.tech (Mechanical engineering), Delhi Technological University, Delhi.
NAVEEN, B.tech (Mechanical engineering), Delhi Technological University, Delhi.
PRIYANSHU VERMA, B.tech (Mechanical engineering), Delhi Technological University, Delhi.
Under the guidance of Dr. Naushad Ahmad Ansari
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Abstract - The paper presents a five-star, four-story hotel
project in Bangalore with 2 basement levels for parking and
services, ground floor for public areas, and 95 guest rooms
from the second to sixth floor. The design focuses on meeting
functionalrequirementswhileavoidingover-sizingequipment,
ensuring cost efficiency, and providing maximum comfort to
occupants. Two HVAC systems (Chill water and VRF) have
been considered for the project, based on international
standards like LEED v4 and ASHRAE 62.1 for maximum cost
efficiency and highest indoor air quality.
Key Words: HVAC, chilled water, energy efficiency, VRF
systems, energy modelling
1.INTRODUCTION
The paper presents a five-star, four-story hotel project in
Bangalore with 2 basement levels for parking and services,
ground floor for public areas, and 95 guest rooms from the
second to sixth floor. The design focuses on meeting
functional requirements while avoiding over-sizing
equipment,ensuringcostefficiency,andprovidingmaximum
comfort to occupants. Two HVAC systems(Chilledwaterand
VRF) have been considered for the project, based on
international standards like LEED v4 and ASHRAE 62.1 for
maximum cost efficiency and highest indoor air quality.
The net use of energy has been on the rise throughout the
world, leading to climate change and increasing greenhouse
gas emissions due to increasedenergygenerationfromfossil
fuels. Even though mitigation measures have been
implemented around the world, significant efforts are still
required to limit the rise in the global temperature to the 2
°C as stated in the Paris Agreement. Theamountof energy
that can be saved in buildings through energy modeling can
vary depending on the specific building and design options
that are evaluated. Building sector accounts for
approximately 40% of the total world final energy
consumption and around one-third of the greenhouse
emissions, therefore, it plays an important roletoreducethe
impact on the environment. However, studies have
shown that energy modeling can lead to significant energy
savings in buildings. By and large, HVAC consumption in
developed countries accounts for half the energy use in
buildings and one fifth of the total national energy use.[3]
2. Air conditioning systems
2.1 Chilled Water Systems:
Chilled water systems are generally used in medium and
large size buildings. These systems act as centralized cooling
systems providing cooling to or even multiple buildings.
Chilled water systems provide cooling to facilities by using
chilled water to absorb heat from the building’s spaces.
The system utilizes a machinery known as Chiller, which
consists of four primary components viz: Compressor,
Evaporator, Condenser, andan Expansion device. These four
fundamental components are present in every chiller,
irrespective of size, shapeandtype.Also,therearethreemain
circuits associated with a chiller, which areveryimportantto
get desired cooling. The first, is the refrigeration circuit,
which is the refrigeration cycle; the second, chilled water
circuit, in which the heat is transferred from the building to
chiller via heated water and then chilled water sent back to
building, and the third, condenser circuit, in which heat is
transferred to cooling tower, acting as a heat ejectionsource.
The chilled water supply (CHWS) is the namegiven tothe
water that exits achiller, typicallyat a temperatureofaround
43 °F (~6°C). This CHWS is then pumped through the chiller
and distributed to various air conditioning units within the
building, such as air handling units (AHUs) and fan coil units
(FCUs). Asthechilledwaterpassesthroughaheatexchanging
coil in these units, it cools the coil, which is then blown with
air by a fan to provide cold air to the building's space. The
supplyair temperatureforAHUsandFCUsistypicallyaround
55 °F (~12°C). After leaving the heat exchanging coil, the
chilled water returns to the chiller, where it is cooled again,
and the cycle repeats. There are two types of chilled-water
systems: air-cooled and water-cooled.

Air-cooled chillers are most often installed outside
buildings and extract heat from chilled water by releasing
heat directly into the surrounding air. Water-cooled chillers
are most often installedinsidebuildings.TheydifferfromAir-
cooled chiller in the fact that it extracts heat from the chilled
water by dissipating it intoa secondisolatedwaterlinecalled
the condenser water line. Condenserwaterflowsthroughthe
chiller and absorbs heat which is then ejected via cooling
tower located outside buildings.
Due to centralized air-conditioning, it providesorganized
configuration and simplifies the maintenance process. They
provide better energy efficiency and cut down money on
energy consumption in the long run.
2.2 Variable Refrigerant Systems:
It is a ductless, large system for HVAC, which uses
refrigerant for both heating and cooling. VRF constantly
controls the amount of refrigerant entering each zone to
ensureoverall comfort and energyefficiency.AVRFsystemis
based on the flow of refrigerant between an external
condensing unit and multiple internal evaporators (usually
fan coil units). Each internal evaporator serves a different
heat zonewithin the building and the refrigerantflowtoeach
evaporator is adjusted based on local requirements. This
provides a high degree of flexibility, allowing the
performance of the outdoor condensertoadapttotheoverall
internal demand, allowing the overall system to operate at
optimum efficiency.
VRF systems achieve high efficiency by making use of
inverter compressors. An inverter system enables the
compressor to ramp up or down as per requirements of
individual space. In a system without an inverter, the
compressor will always run at full capacity. Basically, it's
either on or off. Inverter systems operatingatlowspeedsand
capacities can have significant efficiency gains.
Broadly, a VRF system can be either a two-pipe or three-
pipe system.
The 2-pipe system can cool or heat all zones (heat pump
system). The 3-pipe systemcan heatandcoolsimultaneously
by heating some zones and cooling others. Heat recovery
allows heat from zones requiring cooling to be used to heat
zones requiring heating. This has a higher capital cost, but
heat recovery allows for veryefficient operationandreduces
running costs.
An immediateadvantageofVRFsystemsisreducedenergy
consumption. According to Trane technologies, VRF systems
can save 30-40% energy compared to his traditional HVAC
systems. MostVRFsystemsareinherentlyscalableandcanbe
builtcomponent by component regardless ofthedesiredsize
of the final system. This makes VRF systems ideal for large
new buildings and older buildings undergoing major
renovations and since requirement of ducts is absent, these
systems can be implemented practically anywhere,
regardless of the type of existing HVAC system.
VRF systems are ideal for buildings with multiple areas,
varying heating and cooling requirements, and where good
local control is required, examples, range of commercial
buildings, office spaces,banks,hotelswheresomeroomsmay
be vacant, and others have very high heat demands; etc.
In India, these two air conditioning systems are widely
utilized due to the abundance of materials and parts from
numerous suppliers and manufacturers. To choose the most
efficient and cost-effective option forourbuildingproject,we
will perform a detailedcomparisonofbothsystemsandmake
an informed decision.
3. Occupancies & ventilation requirements
It is extremely important to account forthe occupant density
and ventilation requirements of the occupants in order to
accurately determine the Actual Heat Load of the building.
Following are the occupant density and Ventilation
requirements as per the ASHRAE 62.
Fig 1. Occupancy details from ASHRAE
4. Breakdown of the energy use in buildings:
HVAC systems account for a significant portion ofthe energy
consumption in commercial and residential buildings, with
cooling and heating alone representing up to 50% of the
total energy use. This makes HVAC systems a prime target
for energy efficiencyimprovements.[5]Theexactpercentage
of HVAC's impact on building load depends on various
factors such as the size and location of the building, the
climate, the type of HVAC system used, and the efficiency of
the system.
For example, in a hot and humid climate, the HVAC system
may consume as much as 70-80% of a building'stotal energy
consumption due to the need for air conditioning. In a
temperate climate, the HVAC system may consume less
energy, accounting for 40-50% of total energy consumption.

Fig 2. Building energy use breakdown of a typical office
building
Source: Guide to Best Practice Maintenance and Operation of
HVAC Systems for Energy Efficiency(January2012), Pages36–
37 http://ee.ret.gov.au/energy-efficiency/non-residential-
buildings/heating-ventilation-and-air-conditioning-hvac
It can be easily understood that from the total energy input
of a building, a major and a significant value is taken by the
HVAC systems. By having a control on this value, the
performance of the building can be impacted. The US
Department of Energy reports that energy modelling can
lead to energy savings of up to 40% or more in some cases
[6].
A thorough energy audit and simulation can identify any
operational and design anomalies and lead to improved
performance and reduced energy waste, ultimately saving
cost over time. When designing or renovating a building, it's
crucial to consider the significant impactoftheHVACsystem
on building load. Implementing energy-efficient HVAC
systems and maintaining them properly can minimize their
impact, lower energy expenses, and support a sustainable
future.
5. Steps involved in energy modelling:
There are various steps involved in the process of creating
an energy model in the trace software. These are general
guidelines and the steps involved vary depending on the
scale of the project and the specific process may vary
depending on the version of TRACE 3D Plus being used and
the complexity of the HVAC system.
1. The user creates a new project by opening TRACE
3D Plus and selecting "New Project" from the File
menu. The user inputs a name for the project and
selects a location to save the project file. The user
sets up the project's time zone, weather data, and
other relevant information.
2. The user defines the building by inputting the
building geometry, such as the floor plan, walls,and
roof. The user specifies the type of construction,
insulation, and other relevant information for the
building envelope. The user may also import
existing building information from a CAD program
or other software.
3. The user can also choose which room type will be
the default when a room is drawn. The room will
automatically be assigned the room type template
selected as the default.Room typescanbeexpanded
to view the construction, internal loads, andairflow
templates assigned tothem. Theassignmentscanbe
altered from the drop-down list.
4. The weather tab in the site and building sectionwill
allow the user to view or modify the design
conditions of the selected location as well as view
other locations in the map or the tree the selected
location will show on the top of the tree and the
map will be zoomed in to the specific location
marked with a star.
5. The user will now proceed to thecreatebuildingtab
to draw our building when you click on the create
building tab notice the three options that show g/b
XML import draw building and building wizard.
Upon selecting the image file, you will need to click
a location on the image that will belinedupwiththe
origin. The user can relocate the pictures origin
simply use the origin tool and click a spot on the
image where the new origin will be. The image is
then scaled to match the true dimensions of the
project.
6. Length and width values can be entered whenusing
the drawing tools using these fields will create
rooms or walls. They can also be used to add
windows and other elements in the project.
7. Levels can be added above or below the original
level by simply clicking the plus sign on either side
of the current level indicator. The user can switch
between levels by clicking on the number of the
desired level levels of the building can also be
reordered or deleted.
8. The user defines the HVAC system by choosing the
type of HVAC system they want to model, such as a
central air system, a ductless mini-split system, or
others. The user inputs the system specifications,
such as fan and pump sizes, coil sizes, duct sizes,
and other relevant information. The user may also
import system information from other software or
equipment manufacturer's data.

9. The user defines the loads by inputting the heating
and cooling loads for thebuilding,includinginternal
loads from people, lights, and equipment, and
external loads from windows, roof, and walls. The
user may also import load information from other
software or use default values provided by TRACE
3D Plus.
10. The user runs the simulation and analyzes the
results. They can view air and water flow, air
temperature and humidity, energy consumption,
and other relevant information. They can also
compare the performance of the HVAC system to
industry standards or other design criteria.
11. The user optimizes the system based on the
simulation results by making adjustments to the
HVAC system to optimize its performance and
energy efficiency. They can adjust the system
components, such as fans, pumps, coils, and ducts,
or change the building envelope or load
information.
12. The user repeats the simulation and analysis
process until they are satisfied with the results.
They can make changes to the system or building
information and repeat the simulation as many
times as needed.
13. The user saves the project and exportstheresultsto
share with others or use in other programs. They
can export results in various formats, such as
graphs, tables, and reports, for further analysis or
presentation.
6. Project introduction:
The selected project is a five-star category four story hotel
situated in the city of Bangalore and will comprise of 2
Basements for Parking and Services, Ground floor for Public
areas and 95 Guest RoomsfromSecondFloortoFourthFloor.
The hotel name and brand have not been included for
confidentiality purposes. The hotel plans and structural
details were obtained from the architects. The rates of
electricity and cost of equipment were obtained from HVAC
vendors and contractors. The hotel was analyzed on TRACE
3D PLUS and the total cost was compared for a period of 20
years.
The report describes the project requirement and outlines
the various mechanical and electrical systems to be adopted.
The design philosophyistoensurefulfillmentofallfunctional
requirements in accordance with national and international
standards and codes as well as local by-laws. While fulfilling
the functional requirements, special efforts have been made
towards optimization while ensuringadequacyofequipment
and systems. Through these collective measures, functional
adequacy has been ensured while avoiding over sizing in
equipment and system as all oversized systems/equipment
will cost more to owner, cost more to operate (as oversized
system are inherently inefficient)andmostimportantly,over
designed system is functionally inferior.
We have considered 2 of the most readily available HVAC
systems available in India:
1. Chill water HVAC system
2. VRF HVAC system
The detailed analysis is given below.
Various international standards like LEED v4, ASHRAE 62.1
etc. have been considered while designing the HVAC system,
to ensure maximum cost efficiency, along with ensuring the
highest standard of comfort to the occupants.Adequatefresh
air quantity shall be provided to air-conditioned spaces to
maintain Indoor Air Quality (IAQ) generally as per ASHRAE
standard 62.1-2010.
7. CODES AND REGULATIONS:
The following codes and standards have been used in the
design:
- Accor (IBIS) Engineering Design Guidelines.
- National Building Codes: Building Services 2016
- The American Society forHeating,Refrigeratingand
Air Conditioning Engineers (ASHRAE) standards:
• Ventilation for acceptable indoor air quality 62.1-
2010.
• Energy standards for buildings 90.1-2007.
• ASHRAE handbooks:
• 2018 ASHRAE Handbook, Refrigeration.
• 2019 ASHRAE Handbook, Applications.
• 2020 ASHRAE Handbook,Systemsandapplications.
• 2021 ASHRAE Handbook, Fundamentals.
- AirConditioning,HeatingandRefrigerationInstitute
(AHRI).
- Sheet Metal and Air conditioning Contractors
National Association (SMACNA):
- HVAC duct construction standards, metal and
flexible, 1995.
- Energy Conservation Building Code (ECBC 2017)
- ASHRAE 52.1-1992, 52.2-2007.
- IMD Weather Data.

BUILDING ENVELOPE:
a) ‘U’-value of exposed wall = 0.32
Btu/Hr/ft²/ºF
b) U’-value of roof = 0.0951
Btu/Hr/ft²/ºF
c) Fenestration
i) Public area = ‘U’ value = 0.57
Btu/Hr/ft²/ºF & SHGC = 0.6
ii) Guest rooms = ‘U’ value =0.57
Btu/Hr/ft²/ºF & SHGC = 0.6
8. Hotel Specifications:
Fig 3. Site Location
The site and hotel details are made available to us from the
architects. They specify in detail the various elements,
rooms, lobbies, areas, elevations and give us information on
the occupied and unoccupied areas in the hotel. The project
is a five-star category four story hotel situated in the city of
Bangalore and will comprise of 2 Basements for Parkingand
Services, Ground floor for Public areas and 95 Guest Rooms
from Second Floor to Fourth Floor.
Details of the hotels structure and materials are obtained
from the client and contractors, and they help us in entering
the U – values and shading coefficients of the glass,
partitions, slab, roofs, walls etc. This helps us to get a more
detailed and accurate analysis, further increasing the
accuracy of the results.
Fig 4. Architectural and CAD drawings of hotel and rooms

9. Design Criteria:
9.1 Climatic Design Conditions
The climatic design information as given by
IMD/ASHRAE is used for design, sizing, selecting,
installation, and dehumidification equipment, as well as for
other energy-related processes. 8760 hours (365x24) IMD
weather data has been used for detailedsimulationusingthe
most advanced TRACE-3D PLUS simulation software.
The external environmental conditions used in the
mechanical design are as follows:
Location: Bangalore
Latitude: 12.9716° N, 77.5946° E
Summer
Dry Bulb Temperature : 95.9
Deg. F (35.5 Deg C)
Wet Bulb Temperature : 68.72
Deg. F (20.4 Deg C)
Monsoon
Dry Bulb Temperature : 86.5
Deg. F (30.3 Deg C)
Wet Bulb Temperature : 76.1
Deg. F (24.5 Deg C)
Winter
Dry Bulb Temperature :59.0Deg.
F (15.5 Deg C)
Wet Bulb Temperature :48.0Deg.
F (8.8 Deg C)
9.2 Weather Data:
Fig 5. Weather Data: (a) Daily Temperature Range (b)
Average Temperature Variation Chart (c) Daily Global
Radiation Chart (d) Precipitation chart (e) Diffused/ Global
Radiation Chart (f) Sunshine Duration

10. INDOOR DESIGN CONDITIONS:
To reach comfort conditions and proper environment, it is
necessary to maintain the design at a certain temperature
and humidity within different areas to acceptable levels.
As such, the indoor design temperatureconditionsappliedin
the design of the project shall be according to Table 1 below:
TABLE 1: Temperature,Humidity,ventilationandNCcriteria
Notes:
1. The tolerance levels shown indicate the range of
temperatures due to the operation of the controls
systems.
10.1 BUILDING DESING:
The hotel type was selected to be a standard hotel. This
helped in classifying the various room typesandoccupancies
already available in the TRACE 3DPLUS library as per
ASHRAE guidelines.
The project AUTOCAD or architectural layouts are obtained.
These are then inserted into the TRACE 3DPLUS file to get
reference points to draw the building on a floor-by-floor
basis. This can further help us gain much more detailed and
accurate model of the hotel.
The detailed plans help in classifyingand buildingeachroom
according to specified widths and help to furthersimplifythe
design process. The finishedbuilding matches the important
features of the building perfectly. As far as energy modelling
is considered, it is a highly accurate match.
Fig 6. Building model generation

(f)
10.2 ROOM TYPES:
The next process requires the various rooms generated tobe
dissociated in various room types. The pre-installed room
types are selected from the library and then associated with
each, and every space or room built in the area.
There are various room types to select from including
kitchen, guest room, lobby, corridor, etc. this helps to specify
the room occupancy, ventilation requirement, heating
requirement, heat load etc. This further allows us to
accurately predict and room heating and cooling
requirements, in turn allowing us to calculate the room total
electricity consumption by the HVAC equipment.
10.3 Zone types:
A "zone" is to be a collection of rooms whichshareasingleair
diffuser and/or terminal device(s). For example, if a unit or
AC unit is applied to a zone, all of the rooms in the zone share
the single fan coil terminal unit. All rooms within in a zone
share the parameters in the zone's respective zone type. The
purpose of zone types is to establish the heating and cooling
setpoints, drift points, supply path, return path, and
ASHRAE 62.1 effectiveness ratios at a template level rather
than zone by zone.
Thus, establishing zones allows us to further simplify
calculations, and insert a specific zone type or parameter for
a large number of similar rooms. For e.g., a hotel with 500
rooms can be made a single zone on each floor. Then, if any
changes are required, we only need to edit the individual
floor level zones, rather than all the 500 rooms.
Fig 7. Building zone wise categorization.
(b)
11. HVAC System Alternatives:
TRACE 3D PLUS allows the user to create multiple scenarios
and testing conditions. Thepurposeofacomputermodelisto
test scenarios prior to construction. To facilitate in testing
scenarios, TRACE 3D Plus allows the user to have up to 16
alternatives. The alternatives may be linked, copied, made

new, or any combination of these. For example, The building
may be linked, the systems may be copied for small
changes, the plants may be linked to a different alternative,
and the simulation settings may be completely
different. Alternative 1, is elevated as the main or "base"
alternative throughout many reports.
These alternatives can then be used to generate reports and
comparisons between various scenarios. We create 2
alternatives in this case:
1. Screw chiller
2. VRF system
Both these systems are extremely common in India and are
economical under different conditions.
Fig 8. Alternatives configuration
11.1 SYSTEMS:
There are various types of air conditioning systems we can
choose from in trace. These can be classified into various
types. These must first be accessed from the system library.
The system library has several options to choose from.
1. Variable volume units
2. Constant volume units
3. Heating only units
4. Double duct
5. Chilled beam
And many more such systems. For our consideration, weuse
the constant air volume systems. This is because, constant
volume systems can be easy to control and reduce on capital
costs.
Variable volume systems involve extra control and
equipment. The most important is the modulating dampers
and pressure sensors which are needed to be installed at the
various rooms. This increases capital costs in the form of
increased first costs. Furthermore, this also needs more
complex controlling mechanisms.
We have chosen the following constant volume system.
Fig 9. Sample cooling unit
The selected system consists of various components like an
Outdoor air control and dampers for outdoor and room
return air. The outdoor air is required for ventilation. We
then have the cooling coil by the name SCC -1. The air passes
through this cooling coil and then reaches the room through
the supply damper named D1. SAT 1 refers to the
temperature sensor present in the room.
11.2 Configuring systems:
In order to configure systems, wego to theconfiguresystems
tab. Since the project is a hotel the setpoints are taken
according to ASHRAE standards for internal comfort.
Assigning zones to systems:
Once a system has been designed, it needs zones to be
assigned to it. This is done easily in theassignzonestabofthe
program. Separate systems are applied for areas with
separate zones. We have the following zones made in the
project.
1. Lobby
2. Basement -1
3. Basement – 2
4. First floor
5. Second floor
6. Third floor

7. Fourth floor
8. Fifth floor
9. Sixth floor
10. Ground floor
11. Banquet
12. All day dining.
All these systems have their individual setpoints and
ventilation conditions based on ASHRAE ventilation and
indoor air quality comfort guidelines. The zones can be
assigned to each system easily by the assign zones tab.
Each and every zone can be assigned to various system by
clicking on the system and thenonthezone.Spaceswhichare
unconditioned can also be mentioned here to allow ease in
the selection.
The next is the configurezoneequipment tab.Thisallowsthe
setting up and adjusting of the equipment or Fan coil unit in
the respective rooms or zones. Mostly, 1.5 TR fan coil units
are used in the hotel rooms and the same have been used in
the above project.
11.2 Plant Configuration:
There are prebuilt plant systems in TRACE 3D PLUS. The
program gives the option of automatic plant selection,
however depending on the two systems and the Indian
subcontinent, we select different units and plants.
In the chill water system, there are two loops selected:
1. The chiller loop including two chillers with
manifolded pumps.
2. The cooling tower loop.
Here, water cooled chillers are used as the plant is located in
Bangalore, where the conditions allow the installation of
cooling towers.
Fig 10. Plant configuration
In the VRF system, only one loop is considered as the indoor
units are connected to larger outdoor VRF units.
Fig 11. VRF loop configuration
The given equipment andloopsarethebasisoftheanalysisof
the two alternatives. We now run analysis on both the
systems and get the results in the project summary tabs of
both alternatives.
12 Calculations and Results:
The project summary tab contains the tab for the analysis
and displaying the results. The load report is calculated on
both the selected alternatives. The System Component
Summary report isthemainloaddesignreportforpopulating
specificationsandequipmentschedules.Thisreportprovides
the heating/cooling rate, airflow, air conditions and water
conditions of each coil. The system airflows are calculated
based on the heating and cooling airflows required by the
rooms and zones, plus any system level overrides applied.
System rules are then applied to decide how the heating and
cooling airflows should relate.
The program generates the required load design report. It
consists of:
1. Title Page
2. Room Cooling Loads by Component
3. Room Heating Loads by Component
4. Zone Cooling Loads by Component

5. Zone Heating Loads by Component
6. System Component Summary
7. Design Psychometrics
8. Outside Air and ASHRAE 62.1 Analysis
9. Plant Summary
10. System Cooling Checksums
11. System Heating Checksums
The program generates the reports based on the various
parameters entered and the rooms designed.
13 Reports:
13.1 Project Summary:
The project summary is created by the TRACE software. The
total ventilated or conditioned area is 73,344 ft^2. This is
almost 49.1% of the building area. The weather location
conforms to Bangalore.
13.2 Heat Load Summary:
TABLE 2: Heat Load Summary
TOTAL TONNAGE FOR BASEMENT 2 = 5 TR
TOTAL TONNAGE FOR BASEMENT 1 = 35 TR
TOTAL TONNAGE FOR GROUND FLOOR = 110 TR
TOTAL TONNAGE FOR FIRST FLOOR = 5 TR TFA
TOTAL TONNAGE FOR SECOND FLOOR = 34.4 TR

TOTAL TONNAGE FOR THIRD FLOOR = 37 TR
TOTAL TONNAGE FOR FOURTH FLOOR = 40 TR
The total peak load for the hotel is 266.4 TR. However, since
the cooling required by different zones of the building varies
throughout the day, it is not advisable to select the chillers at
peak load capacity.
We have carried out a detailed simulation for 8760 hours to
provide the block cooling load for the entire hotel, which
comes out to be 254 TR approx.
13.3 Cost Breakdown:
“When selecting an HVAC system, it is important to weigh the
upfront costs (CAPEX) againstthe long-termsavings(OPEX)to
determine the most cost-effective option.[7]”
The cost of a chilled water system and a VRF system can vary
depending on several factors, including the size of the
building, the complexity of the system,and the location.Both
types of systems can be expensive to install, but long-term
costs, such as energy consumption, can be lower for more
efficient systems.
Chill water systems typically have a higher initial cost due to
the need for a central chiller and a network of pipes.
However, they can be more cost-effective in larger buildings
where the cost of the central chiller can be spread out over a
larger area. VRF systems, on the other hand, tend to have a
lower initial cost as they use individual outdoor and indoor
units. However, they can be more expensive to install in
smaller buildings due to the need for multiple outdoor and
indoor units. In addition, VRF systems tend to have lower
energy costs in the long run, as they are more efficient and
offer more precise temperature control.
Overall, the cost of a chill water system anda VRF systemcan
vary depending on the specific needs of the building and the
location, as well as the cost of installation and maintenance.
It's recommended to consult with an HVAC professional to
determine which system would be the best fit for your
building and budget.
13.4 Operational Cost:
In terms of energy efficiency, VRF systems tend to be more
efficientthanchillwatersystemsinsmallerbuildingsbecause
they can adjust the amount of refrigerant flowing to each
indoor unit based on the cooling/heating needs of that area.
Chill water systems on the other hand are more suited for
larger buildings and can be more cost effective for the same.
To determine which system is better suited forourneeds,we
need to deeply analyze the reports and data which we get
from the program. The program analyzes the heating load
generated by the building during various months of the year.
Based on the orientation of the sun, the heating load changes
throughout the year. However, the system must be sized

based on the peak load, as the system must be able to handle
peak capacity generated by the building. The electricity
consumption per month is given below as generated by the
software.
TABLE 3: Monthly electricity consumption by chilled water
and VRF systems : Table format and graphical
representation
Here, we see that the electricity consumption is consistently
less in the case of chill water system, as compared to the VRF
system. The summation for the whole year is calculated.This
difference in kWh is summarized below. The per unit
commercial electricity cost for Bangalore is ₹10/unit.
TABLE 4: Comparison of annual OPEX of chilled water and
VRF systems
E
LE
CT
RICAL
CO
NSUMPT
IO
N
ANNUAL O
PE
RAT
INGCO
ST
(INR/Annum)
T
O
T
AL O
PE
RAT
ING
CO
ST
SAV
ING
S
kW
h Cost of electricity @INR1
0/kW
h INR INR
SCRE
WCHILLE
RSINPARALLE
L 2,532,853.32 25,328,533.25 25,328,533 2,986,1
48
V
RVSY
ST
E
M 2,831
,468.1
2 28,31
4,681
.23 28,31
4,681 RE
FE
RE
NCE
The results of the analysis are summarized in the table given
above. The annual operating cost of the Chill water system is
much lesser than the operating cost of the VRF system. The
cost ofcommercialelectricityconsumptionforthewholeyear
is ₹2,53,28,533 and ₹2,83,14,681 in the case of chill water
and VRF systems. The difference in cost is ₹29,86,148 per
year, asignificant number whenconsideredduringalifespan
of 30 – 60 years. Moreover, asthe costs ofelectricitycontinue
to rise, this gap will further widen.
13.5 Capital/Installation Cost:
A complete comparison is only possible once all the various
aspects of installingthesystemsareanalyzedseparately.This
also includes the cost of purchasingandinstallingthevarious
systems. Only then can the various costs be compared
accurately.
The initial cost for installing the various systems can be
provided by the manufacturers of various equipment once
the heat load has been calculated. The heat load is 255 TR in
the case of our hotel complex. Hence, we size the various
systems according to the tonnage required.
Different manufacturers and suppliers provide equipment
such as chillers and VRF units. Prices for certain common
items are comparable acrossallcompanies,andtheselection
of appropriate pricing is based on quotations from multiple
suppliers. We have compiledasummaryofthecostsinvolved
in the systems.
TABLE 5: Comparison of CAPEX of chilled water and VRF
systems
CHILLEDWATERSYSTEM COST (INR) VRFSYSTEM COST(INR)
Chilledwater pipingwith
inculationandcontrol
valves
9,500,000 Indoor andcoutdoor units 1
7,500,000
Indoor units( Fancoil units
)
1
,800,000
Refrigerant pipingwith
insulation
1
,500,000
Ductingwithinsulation 9,500,000 Ductingwithinsulation 6,500,000
Grills/Diffusers/Dampers 2,000,000 Grills/Diffusers/Dampers 2,000,000
Toilet exhaust system 750,000 Toilet exhaust system 750,000
255TRChiller 6,250,000 Kitchenventilation 2,900,000
320TRCoolingTower 600,000 Associatedelectrical costs 2,200,000
2nos.450gpmSecondary
water pumps
1
,400,000
5nos.450gpmPrimary
water pumps
1
,500,000
2nos.820gpmcondensor
water pumps
1
,000,000
Kitchenventilation 2,900,000
associatedelectrical costs 2,500,000
Heat pimpsfor space
heatingwithaccessories
1
,500,000
Total Cost 41
,200,000 Total Cost 33,350,000

The initial and installation cost can be summarized in the
above table. We see that the chilled water system costs
₹4,12,00,000 and the VRF system costs ₹3,33,50,000. This
difference in cost is approximately₹7,850,000.Thisisquitea
significant amount and must be taken into consideration
while comparing both systems. To make a fair comparison
between the two systems, we need to consider both the
upfront cost and the ongoing cost over the length of the
evaluation period.
*The costs given here are averages of costs and quotations
from various chiller and VRF manufacturers and suppliers,
obtained after sending ourcustomrequirements.Thesecosts
cannot be used as reference to obtain quotations from any
manufacturers or suppliers.
13.6 Comparison:
To summarize, chilled water systems and VRF systems are
both types of HVAC (heating, ventilation, and air
conditioning) systems used for temperature control in
buildings. The chilled water system operates by a central
chiller that cools water anddistributesitviapipestodifferent
air handling units for cooling the air in the building. In
contrast, the VRF system consists of independent outdoor
and indoor units connected by refrigerant lines, providing
greater temperaturecontrol flexibility in specificareasofthe
building.
Buildings have a limited lifespan, with 5-star hotels typically
lasting between 25 and 50 years. 5-starhotelshavealifespan
of 25-50 years. When choosing between options, long-term
costs must be considered, not just initial cost. Both options
were evaluated over 20 years, the typical lifespan of a VRF
system. Results are tabulated below.
TABLE 6: Life cycle cost comparison of chilled water and
VRF systems
CHILLEDWATERSYSTEM COST (INR) VRFSYSTEM COST(INR)
InstallationCost 41,200,000InstallationCost 33,350,000
Lifespanconsidered 20yearsLifespanconsidered 20years
Runningcost per year 25,328,533Runningcost per year 28,314,681
Runningcost for durationof
life
506,570,660
Runningcost for durationof
life
566,293,620
Total Cost 547,770,660Total Cost 599,643,620
The cost of a chilled water system is significantly less when
compared to the VRF alternative when analyzed over a 20-
year life cycle. This difference in cost is substantial, with the
chilledwatersystemcostingapproximately₹5,18,72,960less
than the VRF system forthe operational time.Thissignificant
cost savings is a major factor that allows us to say that the
chilled water system is a better alternative for the hotel
project.
In addition to the cost savings, the chilled water system also
offers other benefits. For example, it is typically simpler and
easier to install, it requires less maintenance and it's more
energy efficient. These benefits can lead to even more cost
savings over time. This is an important consideration when
looking to reduce the impact of the hotel complex on the
environment. In conclusion, the chilled water systemoffersa
combination of cost savings, ease of installation, lower
maintenance requirements and better energy efficiency.Due
to these benefits, the chilled water system has been selected
as the preferred option for the hotel project.
13.7 Further Savings:
Based on above comparison it can be concluded that Water
cooled Screw Chillers in parallel is the better option for our
hotelcomplex. To further reduce electricityconsumption,we
can also pair it with heat exchanger and use the additional
heat to generate simultaneous hot water for domestic use.
This will allow us to use the heat given off by the chill water
system and utilize it for the building. This configuration is
also used in some hotels, but it is not feasible during winter
months, when the chill water system is switched off.
Fig 12. Hot water reuse schematic
13.8 CONCLUSION:
Energy modelling and analysis has allowed us to analyze in
detail the two most used alternatives in order to choose the
most appropriate system for our hotel. Deciding upon the
HVAC system is a big part of project planning as the MEP
rooms, chillers and cooling towers take up a lot of the
valuable space of the hotel. This may cause problems if they
are decided after the hotel structure is made. Furthermore,
the space for ducting and chill water piping is quite different
than the space requirement for the refrigerant piping in VRF
systems, causing structural changes to be made in the
building. Hence, deciding on the HVAC system beforehand is
essential.

Since our hotel is a large-scale project, the TRACE 3D PLUS
data shows that a chill water system is best suited for our
needs. Furthermore, based on the findings of this project, we
conclude that energy modelling is a critical step in
determining the most efficient and cost-effective systemsfor
buildings. By conducting energy modelling, building owners
and operators can gain a deeper understanding of their
energy usage and identify opportunities for improvement.
This approach can help to reduce energy consumption,
decrease operational costs, and improve the overall
sustainability of the building. Therefore, werecommendthat
all building projects should consider energy modelling as a
standard practice to ensure that they are implementing the
most efficient systems for their specific needs.
14 Inference:
LCC or Life Cycle Costing is a methodology used to evaluate
the total cost ofa product or asset over itsentirelifespan.The
goal of LCC is to assess the costs associated with designing,
manufacturing, operating, maintaining, and disposing of a
product or asset, in order to make informed decisions about
its acquisition or development. LCC takes into account all of
the costsassociated with a product or asset over itslifecycle,
including both direct and indirect costs. Direct costs include
the initial purchaseprice,installation,andmaintenancecosts,
while indirect costs may include costs associated with
downtime, energy consumption, and environmental impact.
We have done the life cycle cost analysis which has
successfully allowed us to determine the most optimum
option for the hotel.
This paper also teaches the importance of energy modelling
to ensurebuilding efficiency. “Buildingenergymodelingisan
essential step in designing and operating energy-efficient
buildings. Without energy modeling, building systems and
componentsmaybesizedincorrectly,leadingtoinefficiencies
and higher energy use.” [8]
There are several different types of BEM, including whole-
buildingenergysimulation,envelopeandsystemssimulation,
and daylighting and lighting simulation. Envelope and
systems simulation focuses on specific components of a
building, such as the walls, roof, and windows, and is used to
optimize their thermal performance.
Because every building and project is unique, it is crucial to
conduct energy modeling for each individual project, rather
than trying to apply a one-size-fits-all solution. Through
energy modeling, we can evaluate various options and
determine which systems will be most effective for a specific
project. The modeling will provide a detailed report that can
be used to inform the design and constructionofthebuilding.
It allows for the simulation of a building's energy
performance before it is built, enabling the comparison of
different design options and the selection of the most cost-
effective and energy-efficient solution. Through energy
modeling, we can identify opportunities to reduce energy
consumption and costs, as well as demonstrate compliance
with energy codes and regulations. Additionally, energy
modeling can help to reduce a building's environmental
impact and improve the indoor environment. Furthermore,
energy modeling can also be used to monitor a building's
energy performance after it is constructed and identify
opportunities forfurther energy savings and improvements.
Overall, energy modeling plays a crucial role in the design
and operation of sustainable, comfortable, and energy-
efficient buildings.
The amount of energy that can be saved in buildings through
energy modeling can vary depending on the specific building
and design options thatare evaluated.However,studieshave
shown that energy modeling can lead to significant energy
savings in buildings. For example, a study by the National
Renewable Energy Laboratory found that energy modeling
can lead to energy savings of 20-30% or more in commercial
buildings.[9] Another study by the American Institute of
Architects found that energy modeling can lead to energy
savings of 15-25% or more in residential buildings.[10] In
addition, the US Department of Energy reports that energy
modeling can lead to energy savings of up to 40% or more in
some cases.
Indian government must also start introducing regulation to
ensure all buildings are compliant with the latest standards,
and that energy modellingisdonetoensurethemostefficient
and economical systemsareinstalledtoreduceourimpacton
the environment.
15 References:
[1] United Nations. "The Paris Agreement on Climate
Change," United Nations, Rome, Italy, 2015.
[2] Anderson, J.E.; Wulfhorst,G.; Lang, W. "Energy analysis of
the built environment—A review and outlook," Renew.
Sustain. Energy Rev., vol. 44, pp. 149-158, 2015.
[3] Pérez-Lombard, L.; Ortiz, J.; Pout, C. "A review on
buildings energy consumption information," Energy and
Buildings, vol. 40, no. 3, pp. 394-398, 2008.
[4] Zuo, W.; Zhao, R. "Building energy performance
assessment for sustainable development in China," Energy
and Buildings, vol. 68, pp. 518-526, 2014. (Case study on
building energy performance assessment)
[5] EIA. "Energy use in commercial buildings," U.S. Energy
Information Administration, 2019. [Online]. Available:
https://www.eia.gov/energyexplained/energy-use-in-
commercial-buildings/.

[6] Cheung, T.; Zhang, J.; Hong, T. "Ten questions concerning
occupant behaviorinbuildings:Thebigpicture,"Buildingand
Environment, vol. 128, pp. 284-295, 2018. (Impact of
occupant behavior on building energy performance)
[7] National Institute of Building Sciences. "Life Cycle Cost
Analysis for HVAC Systems," National Institute of Building
Sciences. [Online]. Available: https://www.nibs.org/life-
cycle-cost-analysis-for-hvac-systems/.
[8] Garg, V.; Sharma, A.; Nagpal, G. "Building energymodeling
for energy conservation in buildings: A review," Energy
Reports, vol. 6, pp. 947-957, 2020. doi:
10.1016/j.egyr.2020.02.004
[9] National Renewable Energy Laboratory (NREL). "Energy
modeling for energy efficiency in commercial buildings,"
National Renewable Energy Laboratory (NREL), 2012.
[Online]. Available:
https://www.nrel.gov/docs/fy12osti/54183.pdf.
[10] American Institute of Architects (AIA). "The role of
energy modeling in architectural practice," American
Institute of Architects (AIA), 2017. [Online]. Available:
https://www.aia.org/resources/93606-the-role-of-energy-
modeling-in-architectural.

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Maximizing energy efficiency in hotel HVAC systems: An energy modelling approach to comparing Chilled water and Variable Refrigerant Flow (VRF) systems